Well-established power distribution systems exist throughout most of the United States, and other countries, which provide power to customers via power lines. With some modification, the infrastructure of the existing power distribution systems can be used to provide data communication in addition to power delivery, thereby forming a power line communication system (PLCS). In other words, existing power lines, that already have been run to many homes and offices, can be used to carry data signals to and from the homes and offices. These data signals are communicated on and off the power lines at various points in the power line communication system, such as, for example, near homes, offices, Internet service providers, and the like.
While the concept may sound simple, there are many challenges to overcome in order to use power lines for data communication. Power lines are not designed to provide high speed data communications, are susceptible to interference, and are very lossy at the frequencies used for data communications. Additionally, federal regulations limit the amount of radiated energy of a power line communication system, which therefore limits the power of the data signal that can be injected onto power lines.
Power distribution systems include numerous sections, which transmit power at different voltages. The transition from one section to another typically is accomplished with a transformer. The sections of the power distribution system that are connected to the customers premises typically are low voltage (LV) sections having a voltage between 100 volts (Vrms, 60 Hz, or “V”) and 240V, depending on the system. In the United States, the LV section typically is about 120V. The sections of the power distribution system that provide the power to the LV sections are referred to as the medium voltage (MV) sections. The voltage of the MV section is in the range of 1,000V to 100,000V. The transition from the MV section to the LV section of the power distribution system typically is accomplished with a distribution transformer, which converts the higher voltage of the MV section to the lower voltage of the LV section.
Power system transformers are one obstacle to using power distribution lines for data communication. Transformers act as a low-pass filter, passing the low frequency signals (e.g., the 50 or 60 Hz) power signals and impeding the high frequency signals (e.g., frequencies typically used for data communication). As such, power line communication systems face the challenge of communicating the data signals around, or through, the distribution transformers.
Furthermore, up to ten (and sometimes more) customer premises will typically receive power from one distribution transformer via their respective LV power lines. However, all of the customer premises LV power lines typically are electrically connected at the transformer. Consequently, a power line communications system must be able to tolerate the interference produced by many customers. In addition, the power line communication system should provide bus arbitration and router functions for numerous customers who share a LV subnet (i.e., the customer premises LV power lines that are all electrically connected to the LV power line extending from the LV side of the transformer) and a MV power line.
In addition, components of the power line communication system, such as the distribution transformer bypass device (PLB), must electrically isolate the MV power signal from the LV power lines and the customer premises. Furthermore, a communication device of the system should be designed to facilitate bi-directional communication and to be installed without disrupting power to customers. These and other advantages are provided by various embodiments of the present invention.